Richard M. Daley

Evan Vucci/Associated Press

Richard M. Daley, nicknamed Chicago’s “Mayor for Life,” was first elected in 1989 and re-elected in 1991, 1995, 1999, 2003 and 2007. In September 2010, with no prelude or fanfare, Mr. Daley announced that he would not seek re-election.

For the better part of 56 years — for better and for worse — the Mayors Daley ran Chicago: first, Richard J. Daley, the former mayor’s father, from 1955 to 1976, when he died in office, then Richard M. Daley, from 1989 to 2011. He was the longest-serving mayor in the history of the city, surpassing his father.

Historians may see that as a theme. The younger Daley, born in 1942, inherited a city riven by racial strife and mired in official corruption. Even if he failed to eliminate those ills, some would say, he turned the city into an economic success story, paying particular attention to beautifying Chicago’s aging core.

The younger Mr. Daley promoted the city’s business, tourism, culinary and art industries in a way that positioned Chicago to compete with American cities better known for such things, like New York and San Francisco.

Mr. Daley presided over Chicago’s shift from a manufacturing economy to one based on the service industries and finance, keeping the city afloat and thriving as others in the Midwest faltered. He cloaked downtown in green, creating parks and environmentally friendly roofs, and planting flowers with a gardener’s touch.

He also tore down some of what his father built, sometimes literally. For instance, the first Mayor Daley built the high-rise public housing projects that became a model for the rest of the country. The second Mayor Daley began tearing down some of the largest projects — considering them a failed experiment in public housing — and many cities followed his example.

Chicago stalled in the mid-1980s, and the government broke down into what was known as the Council Wars, where white aldermen blocked the reform agenda of Harold Washington, the city’s first black mayor, turning City Hall into a tumultuous battleground of coarse racial politics. Even Mr. Daley’s critics concede that he did much to calm the racial strife, promoting minorities and women and gaining a reputation as someone who believes in diversity.

Despite both Daleys’ administrations being plagued by corruption, both are also credited with preventing Chicago from experiencing the ignominious slide of other Midwestern cities like Cleveland, Detroit and St. Louis. Coming out of the midcentury, Chicago was known mostly as hog butcher to the world.

Over the decades, the Daleys (and the fewer than a half-dozen intervening mayors) diversified the city, keeping it growing as comparable Rust Belt cities shrank. The elder Daley built O’Hare International Airport, securing Chicago’s place as a national transportation hub in the modern era, as it had been in the age of railroads. The younger Daley expanded O’Hare, a mission that continues to this day.

In 2009, Mr. Daley suffered what was perhaps his most significant recent defeat not in an election but when Chicago lost its bid to host the 2016 Olympic Summer Games. He emerged globally as the city’s promoter in chief and suffered a blow when Chicago was among the first cities eliminated.

Prior to serving as mayor, Mr. Daley served in the Illinois Senate and then as the Cook County State’s Attorney. He also served as the 11th Ward Democratic committeeman after his father died.

Perhaps the very definition of a strong mayor with almost absolute command, Mr. Daley leaves no apparent political heirs. He was widely expected to seek a seventh term without serious opposition. Few had been willing to challenge him.

In 2010, President Obama gave his blessing for Mr. Emanuel, his chief of staff, to pursue the race for mayor.

Mr. Daley and Mr. Emanuel are Democrats, political allies and personal friends. Long ago, Mr. Emanuel raised money for one of Mr. Daley’s campaigns. Though Mr. Daley never publicly chose sides in the mayoral race, he is widely believed to have given a tacit nod to Mr. Emanuel.

Mr. Daley said that although the news media and others might seek some hidden reason for his decision, there was none. “In the end, this is a personal decision,” he said. “No more, no less.”